The lifesaving secret hidden inside a horseshoe crab's blue blood

The crab’s unique blue blood reacts to dangerous bacteria. That makes it a powerful tool when testing vaccines and other injectable medicines for contamination.  “If you’ve had an injection, if you had an infusion, if you’ve had dialysis, if you’ve ever had a medical device, a vaccine, that [has] been tested for endotoxins using horseshoe crab blood,” Bolden explained. Each year, around 200,000 crabs are caught for the biomedical purposes each year in Massachusetts. Nationwide, that number has tripled over the last 20 years, according to 2024 data from the Atlantic States Marine Fisheries Commission.  While the crabs’ blood helps keep medicine safe, it also comes at a cost. The Atlantic States Marine Fisheries Commission has historically estimated that about 15% of crabs die as a result of the biomedical process.  “Without a doubt there is a negative impact on crabs through going through this process,” Bolden said.  Horseshoe crabs don’t just help the biomedical industry, their eggs serve as a main source of food for other coastal wildlife. Scientists explain an impact to the horseshoe crab population creates a ripple effect throughout the environment.  “You’re impacting migratory shore birds and sharks and turtles and spore fish, right? It’s all connected,” Bolden said.  Scientists say there may be a better way to protect both people and horseshoe crabs. They have created a lab-made alternative to test medicines, so no crabs are needed. “It is the exact same protein, it is just made through biotechnology,” Bolden said.  Bolden said scientists at Eli Lilly tested thousands of samples on hundreds of different products and determined the alternative performs the same or better than purified horseshoe crab blood does.  Starting in 2016, Eli Lilly started to switch its testing to the lab-made version.